Operando NMR methods for studying electrocatalysis

The combination of electrochemical measurements with spectroscopic characterizations provides valuable insights into reaction mechanisms. Nuclear magnetic resonance (NMR) spectroscopy, as a powerful technique due to its atomic specificity and versatility in studying gas, liquid, and solid, allows the study of electrolyte solution, catalyst and catalyst-adsorbate interfaces. When applied in operando, NMR can offer molecular-level insights into various electrochemical processes. Operando NMR has been applied extensively in battery research, but relatively underexplored for electrocatalysis in the past two decades. In this mini review, we first introduce the operando electrochemical NMR setups, categorized by different probe designs. Then we review the applications of operando NMR for monitoring the electrolyte solution and the catalyst-adsorbate interface. Considering the high environmental impact of electrochemical conversion of CO2 into value-added products, we zoom in to the use of operando NMR in studying electrochemical CO2 reduction. Finally, we provide our perspective on further developing and applying operando NMR methods for understanding the complex reaction network of Cu-catalyzed electrochemical CO2 reduction.